Sydney: Australian professional motorcycle racer, two-time MotoGP world champion, Casey Stoner, announced that he will retire from Grand Prix racing at the end of season due to "family reasons", local media reported on Friday.

The 26-year-old Australian made his announcement at a press conference before the 2012 French Grand Prix, the Australian Broadcasting Corporation (ABC) reported.

"After a long period of thought and numerous discussions with my wife and family, I have decided to stop competing at the end of the season," Stoner said.

"After so many years taking part in this sport that I love, and with all the sacrifices that I have had to make, I no longer have the passion to continue and I think that it is best to stop."

Stoner, who has won 35 MotoGP races in his career, is best known for wining the world title twice in 2007 and 2011.